Means for controlling electric arcs



Jan. 16, 1951 K. LERSTRUP MEANS FOR CONTROLLING ELECTRIC ARCS 2Sheet-Sheet 1 Filed Feb. 5, 1947 INYENTOR ka/oX t/wp y2 ATTORNEY K.LERSTRUP MEANS FOR CONTROLLING ELECTRIC ARCS Jan. 16 1951 Filed Feb. 5,1947 2 SheetsSheet 2 lNv ENTOR (95/01/01 i/Q/QVM BY M ATTORNEY PatentedJan. 16, 1951 UNH'EED STATES PATENT OFFICE MEANS FOR CONTROLLINGELECTRIC ARCS Karl Lerstrup, Milwaukee, -W-is., assignor to Allis-Ohalmers Manufacturing Company, Milwaukee, Wis., acorporation ofDelaware Application February 5, 19517, .Serial,No.'7 26,5,8f7

4 Claims.

This invention relates to the control of electric arcs and moreparticularly to the control of arcs on are runners ,and arcs formed bythe opening of electric switches. The principal object of the inventionis the provision of new and improved methods of and means forcontrolling electric arcs, and new and improved electric switches.

A more specific object is the provision of new andimproved ways ofcontrolling an electric are so that the arc will berapidly moved andrapidly extinguished. To attain that object it is necessary that theincipient arc be caused to move in-a desired direction, and theestablished arc be caused to move and move rapidly in a desired.direction. Itis a further object to attain these resultswithout theuse. of the usual blowout coils ormagnets and in a more efficient way.

Other objects will appear as the description of the invention proceeds.

The novel features of the invention and how the objects areattained willappear from this specification and the accompanying drawings showingseveral embodiments of the invention and forminga part ofthisapplication, and all these novel features are intended to be pointedout in the claims.

.In the drawings:

Fig. 1 is a side elevation, partly fragmentary, of apparatus embodyingthe invention, this apparatus including a circuit breakerprovided witharc runners;

Fig. 2 is a side elevation, on-an enlarged scale, of a detail of themovable arcing contact usedin the embodiment of Fig. 1, showing itsrelationto the relatively stationary arc runners fragmentarily shown;

Fig. 3 is a bottom view of the movablearcing contact shownin Fig. 2;

Fig. 4 is a section, on an enlargedscale, taken on the line IV--IV ofFig. 2, looking in the direction of the arrows;

Fig. 5 is a fragmentary, section, on an enlarged scale, taken on theline VV ,of Fig. 1

Fig. 6 is a fragmentary view of a detailv of Fig. 1 looking through theplane VI--VI in the direction of the arrows;

Fig. '7 is a side elevation, partly schematic, of another embodiment ofthe invention in the form of a circuit breaker;

Fig. 8 is a view of an end of one of the arc runners of Fig. 7 t aken atright angles to Fig. 7;

"Fig. 9 is a side elevation, partly schematic, of another embodiment ofthe invention inthe torm of a circuit breaker;

Fig. 10 islafront elevation oft-he circuitbreake how nfi 9; and A Figs.11, 12, 13, 14, 15 and 16 are cross-sectional views of respectivelydifferent are runners em boolying the invention.

Referring f rst to Figs. 1 through 6, the circuit breaker here showncomprises relatively stationary ,main contacts 29, 2] adapted to bebridged by a relatively movable main contact 22, the latter beingheld byablock 23, which may be moved toward and away from the relativelystationary contacts "20, 2! b-y an operating rod or Idember 24.

Thestationary main contacts 20, 21 may be supported iromfinsulatingsupports 25, 26 in any suitable way, and may-be connected to conductors21,28, respectivelyiorming part of the circuitto be controlled. Theconstruction and arrangementofthe maincontacts 20, 2|, 22 is notmaterial as far as the present invention is concerned.

The circuit breaker further comprises relativelyfstati onary arcingcontact portions 29, -30

adapted :to be abuttingly engaged by a relatively movable arcing contact3|, The contact 3| is heresh own as of inverted heart-shaped orgenerally triangular form, the triangle having an apexdisposedbetweenthe relatively stationary arcin contacts; 29, 36, with sides 32, 33'adapted to engage the contacts 29.30. The contacts 29, 3 U, 3;l may bemade of copper or any other suitable metal and, if desired, may-beprovided at-the 'places of engagement with insets -34, 35'-and 36,

gagement where the portions carry current'to and from the arc, they nakean angle of substantially less than 90 and desirably lessthan The sameis'true with respect to the portions 30,-33.

T-he apex of the triangular contact 3| has a split;38, and, as maybeseen in Figs. 2 and 3 the side of the triangular contact opposite the,apex also has a, ,split s9.,.. dividing that side into two partsfllLt Ibutunless it is desired to increase the magnetic efiect of currentflowing in the triangular contact 13!, as will appear, the split 39 maybe omitted and the side portions, 4| made integral.

Th co ac 3 114% h u ort and m v in any suitable way. As here shown thecomposite side 4U4|-is fastened by an insulating clamp 42 to aninsulating support 43 through which freely pass a pair of headed studs44, one pair on each side of the composite side 4|l--4|. The studs 44are fastened in the block 23 and springs 45 may be provided for biasingthe support 43 to the position in which the insets 35, 36 are inengagement with the insets 34, 31. The lost motion connection providedby the studs 44 and support 43 permits the springs 45 to maintain thecontact 3| in engagement with the contacts 29, 35 after the bridgingmember 22 has been moved out of engagement with the contacts 2|], 2|.

Desirably, a member of magnetic material 50, here shown as having twoflat portions joined at is disposed within and complementary to theinside surfaces of the sides 32, 33 of the contact 3|; from the contact3| by an insulating member 52, here shown as covering the entire insidesurface of the contact 3|.

The member of magnetic material 50 may be laterally sup-ported in anysuitable way, as by i an insulating block 53 shown in Fig. 4 but omittedin Figs. '1, 2 and 3 to more clearly show the otherwise hidden parts.The block 53 may be of generally triangular form complementary to theinside surface of the insulating members 52 and fastened thereto.

The block 53 has a channel 54 for receiving the magnetic member 50.

When the split 39 is used, the parts 40 and 4| may be electricallyconnected by an insulated conductor 55 disposed in a recess 55 in theportions 32, 33, 4|], 4| of the triangular contact 38. One bared end 5!of the conductor 55 is disposed in a hole 58 in the portion 40, radiallyoutside of the recess 55, and the other bared end 59 of the conductor 55is disposed in a hole 60 in the portion 4|. The ends 5I, 59 are solderedor otherwise suitably fastened and electrically connected in therespective holes 58, 59. The conductor 55 is here shown as soconstructed and arranged that it makes three turns from the end 51 tothe end 59. From the end 51 the conductor goes to the level of therecess 56, makes a turn in the uppermost position, as viewed in Fig. 3,then crosses to the central position, makes a turn, then crosses to thelowermost position, and makes a turn to .the end 59.

It will be apparent that a conductor making any other desired number ofturns may be used. a

The portion 29 of the stationary arcing contact is here shown asintegral with a generally horizontal portion I5 which may beelectrically immediately connected to the contact 29 or the conductor21, or it may be mediately connected as will appear. The portion 29 isalso here shown as integral with an arc runner portion II which extendsupwardly at an angle toward the left as viewed in Figs. 1 and 2.

The portion II of the arc runner is here shown as joined to a generallyvertically extending portion I2 which in turn is shown as joined to aneye or loop I3 as may be seen in Fig. 6. The loop I3 is here shown assubstantially circular but having a terminal end I4 spaced from thebeginning of the loop. The portions 19, 29, I2 and I3 may be of circularsection or other desired Disposed about the arc runner and also aboutThe member 59 is here shown as insulated the portion 29 is magneticmaterial here showii as separate, longitudinally spaced sections I5, thecross-sectional form of which may be seen in Fig. 5. As here shown thesections I5 are of clip form having a body I5 extending more than 189around the conductor in question, in Fig. 5 the arc runner portion II.The sections I5 are here shown as provided with outwardly flaring wingsTI. The sections I5 may be insulated from the respective conductorportions with which they are associated by insulating material I8. Thus,the sections I5 comprise a plurality of bodies of magnetic materialdisposed alongside of and in laterally confronting relation to the arcrunner I I, and are so arranged that the are runner II extends in eitherdirection past the sections I5.

If desired the portion 29 and that part of the portion I0 at the rightof support 25, and the arc runner portions I|, I2 may be backed by asuitably shaped insulating block I9 fastened to the support 25, as byscrews 80, and may be laterally supported by insulating plates 8|fastened to the block I9 as by screws 82. The parts I9, 9| arefragmentarily shown in the left half of Fig. 1 and entirely omitted inthe right half, for the sake of clarity.

Disposed within the loop I3, a magnetic core 83 is here shown, whichcore may have a flange 84. The loop I3 is insulated from the core 83 andflange 84 by a layer of insulating material 85. The flanged core issupported in any suitable way from the support 25.

As hereinbefore mentioned the arcing contact portion 29 and the arcrunner II, including also the arc runner portions I2, 13, may beprovided with a longitudinally extending recess 90. The recess 99 isclearly shown in the portion II in Fig. 5, and in the portion 30(corresponding to the portion 29) in Fig. 4.

Referring again to the left side of Fig. 1, disposed in the recess 99 isan insulated conductor 9 i, one end 92 of which is mechanically andelectrically connected to the contact 20, and extends in the recess 99in the portion I0, 29, II, I2, I3 and emerges from the portion l3 at aplace spaced somewhat from the end I4, and has its other end 93mechanically and electrically connected to the portion I9. Instead ofhaving the insulated conductor 9| in a slot or recess 90, it may bedisposed, as in the case of conductor 9|c, Fig. 15, in a longitudinalhole 900 in a runner I I0 or analogous part. On the other hand therunner or analogous part may be of solid section and the auxiliaryconductor may be disposed alongside such construction being shown inFig; 16 where ,IId is a runner and 9|d is the insulated auxiliaryconductor. The construction comprising a slot or recess is preferred.

The right side of Fig. 1 is the same as the left side hereinbeforedescribed except of course that the conductor 9| has its end 92connected to the contact 2|. In the left side of Fig. 1 some of thelower clips I5 have been broken away, whereas in the right side of Fig.1 some of the upper clips I5 have been broken away to show otherwisehidden parts. If desired, the usual arc barriers (not shown) may beprovided between the runners II.

The operation of the embodiment of Figs. 1 through 6 is as follows.Assume that current is flowing from the conductor 21 to the conductor29through the contact 20, bridging member 22 and contact 2|, and thatthe rod 24 is moved downward thereby interrupting the path for cur-.-

5 rent through the bridging member 22. Current then continues to flowfrom point 92 through. conductor 95 to point 93, through portion Ithrough portion 29 acrosscontact points 34, 35 downward through portion32 through portion 49 to end of conductor 55, through conductor 55 tothe end 53 thereof, thence through portion 4|, then upwardly throughportion 33 to contact point 33 across to point 3's downward throughportion 3i through portion Til, and from terminal 93 through conductor9I to terminal 92 and conductor 28.

By reason of the acute angle made by the parts of the portions 29 and 32just below the contact points 3 3, 35, that is, on the arc-trailing sideof these points, and the fact that the current flow is in oppositedirections in these parts, an intense magnetomotive force is providedinthe space defined by that angle. This magnetomotive force ismultiplied, in the embodiment of Fig. "1, by the conductor 9i, thecurrent in which it is collateral to and in the same direction as thatin the portion 29, and is further multiplied by the conductor 55, thecurrent in which it is collateral to and in the same direction as in theportion 32. The magnetic flux produced by the magnetomotive force ismultiplied by the provision of the magnetic members '55 and the magneticmember Ell, which members greatly reduce the magnetic reluctance of theflux path around the portion 29 (and the conductor iii if present) andsimilarly greatly reduce the reluctance of the flux path around theportion 92 (and the conductor 55 if present). What has been statedapplies as well to the similar parts on the right side of Fig. 1.

Accordingly, when the contact 35 is moved downwarc, disengaging thecontact points 35, 36 from the points 3 3, 3?, the incipient arcs formedat the places of disengagement are being powerfully acted on by themagnetic fluxes hereinbefore referred to whereby the arcs are caused tomove upward, the leithand are continuing upward with its terminals onthe lefthand runner it and the portion 32 respectively, and therighthand' arc continuing upward with its terminals on the portion 33and th righthand runner 7! respectively.

The right and lefthand arcs move upward rapidly and leave the portions32, 33, uniting at the middle into a single are extending from thelefthand runner i l to the righthand runner 'i i. This single arc, andespecially the foot points or terminals thereof, is powerfully acted onby the magnetic flux produced by the current in the arc runners H at thetrailing side of the arc erminals, causing the arc to move rapidly up-.ward. If the arc has not been extinguished by the time its terminalsreach the loops I3, the terminals will be caused, by the magnetic fluxproduced by the current in the loops at the trailing side of the arcterminals, to move along the loops. When the arc terminals reach theends l4, the terminals will jump to the beginnings of the loops l3 andagain run around the loops until the arc is extinguished. It will beapparent that the arc terminals will, accordingly, not remain at onepoint, and severe burning of the arc runners and especially the ends ofthe arc runners is prevented.

The various parts of magnetic material hereinbefore described serve notonly to reduce magnetic reluctance but to aid in dissipation of heatproduced by the arc. Sectionalizing that part of, the magnetic materialcomprised in the clips I5 prevents current from following the magneticmaterial if the arc should burn to one of the clips.

Referring now to the embodiment of Figs. '7 and 8, there is here shown aswitch comprising a movable member 94 swingable about a pivot 95. Themovable member 94 is shown in closed position in which it engages aconducting portion 29a continuing upwardly as an arc runner Ila. It willbe noted that the angle defined between the contact 94 and portion 29ais an acute angle as hereinbeiore described with reference to theportion 29 and the contact portion 32 of Fig. 1. The movable member94 isconnected by a conductor 96 to the circuit conductor 28a, and when themovable member 94 is moved to the dotted line position an arc is firstdrawn between the portion 29a and the member 94, the righthand terminalof the arc being then transferred to the righthand runner I la. The arethen rises along the runners Na and if not sooner extinguished continueson the loops 13a until extinguished.

In Figs. 7 and 8 parts corresponding to similar parts in Fig. I bear thesame reference numerals with the sufi-lx a, but in Figs. 7 and 8 theconducting parts are of solid section and no auxiliary conductors, suchas 55 and 9| of Fig. 1, are provided. Also no magnetic materialconstructed and arranged for reducing magnetic reluctance is provided. Aconstruction of the type shown in Figs. 7 and 8 may be employed wherethe operating requirements are met thereby.

Figs. 9 and 10 show a switch comprising a stationary main contact 9!with which a movable main contact 93 is cooperable. The movable contact9B is shown as carried by a member 99 pivoted at N19 to a terminal IN.The contact 91 and terminal HlI may be carried in any suitable way by.an insulating support I02. The member 99 carries an arcing contact I03engageable with a relatively stationary arcing contact portion 29b. Heretoo "the angle defined between the portion 29b and the contact W3 is anacute angle. Above the point of engagement the contact I93 may beprovided with an outwardly bent portion i594 of any desired length. Thecontact I03 may be made flexible, constructed and arranged in any way sothat it will leave engagement with the contact portion 291) after themain contacts 91, 98 are opened.

The portion 29b is continued upwardly as an arc runner lib which as hereshown is terminating in a vertical portion 12b but unlike these similarparts in Figs. 1 and '7, no loop is provided at the end of the portion12?). In the embodiment shown in Fig. 9, the portions 19b, 29b, 1 I11and 12b are provided with longitudinal recesses in which, as in theembodiment of Fig. '1, a conductor 9Ib is disposed, this conductorhaving the end emerging from the recess in the portion 191) connected tothe contact 9? and the other end connected to the portion 19b. Theeffect is the same as described in connection with Fig. 1.

Fig. 11 shows a cross-section of an are runner I05 which is held byinsulating enamel I96 or other suitable material in a longitudinalgroove or recess in a magnetic member I 01 of any desired suitablecross-section. The are runner lilimay, if desired, be made of such smallcross-section that it would be inadequate to withstand the heat of thearc and/or not mechanically stiff enough to be desirablyself-sustaining. When so designed, the arc runner I may carry an arccurrent capable of generating a quantity of heat in the arc runnergreater than the heat required for fusing the arc runner. However, sincethe runner 105 is mechanically supported by and in heat transferrelation to the magnetic member lOl, it need not be selfsustaining andthe heat of the arc will be dissipated and, both because of its smalldiameter and because the member 101 is magnetic the reluctance of thepath around the runner will be of low value. Insulating enamel IllBa mayalso be applied to the front surface of the member I01.

In general, irrespective of the particular embodiment of Fig. 11, it isadvantageous to make the cross-section of-the arc runner as small aspossible because the magnetic flux path around the runner is decreased.Also, the mechanical force of the magnetic field produced by current inthe runner and acting on the are is proportional to the square of thecurrent, and the force at the surface of the runner, which is ofgreatest importance, is inversely proportional to the length of theshortest magnetic path around the runner, Thus it is advantageous to usean arc runner of as small, circular cross-section as possible, and, inaddition, to increase the permeability of the fiuX path around therunner. Whether or not the magnetic material used to increase thepermeability of the flux path functions to dissipate heat from therunner, it can be constructed and arranged to stiffen and mechanicallystrengthen the runner.

Fig. 12 shows a cross-section of an arc runner I08 disposed in alongitudinal groove or recess in a member H19 of magnetic material. Amember- I it of self-sustaining insulating material may be interposedbetween the runner 498 and the surface of the groove, the member hisand. i lating material liil being cemented together in any suitable way.The member ill] may be pro vided with outwardly flaring wings iii to protect the member H19 from the arc.

Fig. 13 shows a cross-section of an arc runner H2 of flatcross-sectional form which may provide a desirably large cross-sectionalarea. Disposed about the runner I 12 is a clip l 63 of magnetic materialconforming to the outline of the runner for most of its circumferenceand having outwardly flaring wings H t. A layer of insulating material Hcovering the inside surface of the clip H3, H4 is provided. Thiscombination provides a runner 12 of desired larger crosssectional areaand at the same time a flux path around the runner having a lowreluctance.

Fig. 14 shows a cross-section of a runner it of generally circularcross-section having a longitudinally extending lateral extension or ribii! here shown as of generally rectangular crosssectional outline.Disposed about the runner i it, I ll is a clip i it? of magneticmaterial conforming generally to the outline of the runner for most ofits circumference and having outwardly flaring wings H9. The runner maybe of suificient cross-sectional area to provide for cooling and due tothis factor and/or due to the presence of the rib Hl is of sufficientmechanical strength and stiffness without the clip M3, the latterserving, however, to reduce the magnetic reluctance of the flux patharound the runner. Self-sustaining insulating material I23 protects thesurface of the wings 1 i9 and is interposed between the clip proper H3and the runner H6.

From the foregoing it will be apparent to those skilled in the art thatthe illustrated embodiments of the invention provide new and improvedmethods of and means for controlling electric .arcs and new and improvedelectric sw tch and accordingly accomplish the objects of the invention.On the other hand, it will also be obvious to those skilled in the artthat the illustrated embodiments of the invention may be variouslychanged and modified, or features thereof, singly or collectively,embodied in other combinations than those illustrated, without departingfrom the spirit of the invention, or sacrificing all of the advantagesthereof, and that accordingly the disclosure herein is illustrativeonly, and the invention is not limited thereto.

It is claimed and desired to secure by Letters Patent:

1. An arc runner comprising, a continuous conductor means forming a pathfor a movable terminal of an electric arc and means for reducing themagnetic reluctance of the flux path around said conductor means withrespect to magnetic flux generated by current flow in said conductormeans, said reluctance reducing means including a plurality of bodies ofmagnetic material disposed opposite the terminal of the are alongside ofand in laterally confronting relation to said conductor means, saidconductor means extending past said magnetic bodies, the adjacent saidbodies being spaced from each other longitudinally with respect to saidconductor means for substantially restricting said are to said conductormeans during movement of said are terminal.

a. An electric switch, comprising: arcing contacts engageable at a givenplace of contact and relatively movable away from each other to strikean electric are at said. place; means for increasing the magnetomotiveforce acting on the are at the trailing side thereof; at least one ofsaid contacts forming an arc runner for a movaole terminal of anelectric arc, said runner including means for continuously shifting thearc to shut the spot of junction between the arc and said are shiftingmeans while the arc exists, said are shifting means comprising asubstantially circular conducting loop at the end of said runner; andmeans for reducing the magnetic reluctance of the flux path around saidrunner with respect to magnetic flux generated by current flow in saidrunner.

3. An electric switch, comprising: arcing contacts engageable at a givenplace of contact and relatively movable away from each other to strikean electric are at said place; means for increasing the magnetomotiveforce acting on the are at the trailing ide thereof; at least one ofsaid contacts forming an arc runner for a movable terminal of anelectric arc, said runner including means for continuously shifting thearc to shift the spot of junction between the are and said are shiftingmeans while the are exists, said are shifting mean comprising asubstantially circular conducting loop at the end of said runner; andmeans for reducing the magnetic reluctance of the flux path around saidrunner with respect to magnetic flux generated by current how in saidrunner, said reluctance reducing means including a plurality of bodiesof magnetic material disposed opposite the terminal of the arc alongsideof and in laterally confronting relation to said runner, said runnerextending past said magnetic bodies, the adjacent said bodies beingspaced from each other longitudinally with respect to said runner forsubstantially restricting said are to said runner during movement ofsaid are terminal.

4. Electric arc extinguishing means, comprising: means for lengtheningthe are including an 9 arc runner providing a path along which the arccan move toward the 'end of the runner as the arc is lengthened, saidrunner having an end comprising a substantially circular conducting loopfor supplying a magnetic field to continually shift the spot of junctionbetween the arc and said 100p while the arc exists; and magnetic meanspositioned within said loop for strengthening said magnetic field.

KARL LERSTRUP.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 701,577 Klein June 3, 1902 NumberNumber 15 71,393 114,061 368,645 514,100

